zeppelin/r/_tools/checkstyle.xml

<?xml version="1.0" encoding="UTF-8"?>
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<!DOCTYPE module PUBLIC
    "-//Puppy Crawl//DTD Check Configuration 1.3//EN"
    "http://www.puppycrawl.com/dtds/configuration_1_3.dtd">

<!-- This is a checkstyle configuration file. For descriptions of what the 
	following rules do, please see the checkstyle configuration page at http://checkstyle.sourceforge.net/config.html -->

<module name="Checker">

	<module name="FileTabCharacter">
		<!-- Checks that there are no tab characters in the file. -->
	</module>

	<module name="NewlineAtEndOfFile">
		<property name="lineSeparator" value="lf" />
	</module>

	<module name="RegexpSingleline">
		<!-- Checks that FIXME is not used in comments. TODO is preferred. -->
		<property name="format" value="((//.*)|(\*.*))FIXME" />
		<property name="message"
			value='TODO is preferred to FIXME.  e.g. "TODO(johndoe): Refactor when v2 is released."' />
	</module>

	<module name="RegexpSingleline">
		<!-- Checks that TODOs are named. (Actually, just that they are followed 
			by an open paren.) -->
		<property name="format" value="((//.*)|(\*.*))TODO[^(]" />
		<property name="message"
			value='All TODOs should be named.  e.g. "TODO(johndoe): Refactor when v2 is released."' />
	</module>

	<!-- <module name="JavadocPackage"> - Checks that each Java package has 
		a Javadoc file used for commenting. Only allows a package-info.java, not 
		package.html. </module> -->
	<!-- All Java AST specific tests live under TreeWalker module. -->
	<module name="TreeWalker">

		<!-- IMPORT CHECKS -->

		<module name="RedundantImport">
			<!-- Checks for redundant import statements. -->
			<property name="severity" value="error" />
		</module>
		<!-- <module name="ImportOrder"> Checks for out of order import statements 
			<property name="severity" value="warning"/> <property name="groups" value="com.google,android,junit,net,org,java,javax"/> 
			This ensures that static imports go first <property name="option" value="top"/> 
			<property name="tokens" value="STATIC_IMPORT, IMPORT"/> </module> -->
		<!-- JAVADOC CHECKS -->

		<!-- Checks for Javadoc comments. -->
		<!-- See http://checkstyle.sf.net/config_javadoc.html -->
		<module name="JavadocMethod">
			<property name="scope" value="protected" />
			<property name="severity" value="warning" />
			<property name="allowMissingJavadoc" value="true" />
			<property name="allowMissingParamTags" value="true" />
			<property name="allowMissingReturnTag" value="true" />
			<property name="allowMissingThrowsTags" value="true" />
			<property name="allowThrowsTagsForSubclasses" value="true" />
			<property name="allowUndeclaredRTE" value="true" />
		</module>

		<module name="JavadocType">
			<property name="scope" value="protected" />
			<property name="severity" value="error" />
		</module>

		<module name="JavadocStyle">
			<property name="severity" value="warning" />
		</module>

		<!-- NAMING CHECKS -->

		<!-- Item 38 - Adhere to generally accepted naming conventions -->

		<module name="PackageName">
			<!-- Validates identifiers for package names against the supplied expression. -->
			<!-- Here the default checkstyle rule restricts package name parts to 
				seven characters, this is not in line with common practice at Google. -->
			<property name="format" value="^[a-z]+(\.[a-z][a-z0-9]{1,})*$" />
			<property name="severity" value="warning" />
		</module>

		<module name="TypeNameCheck">
			<!-- Validates static, final fields against the expression "^[A-Z][a-zA-Z0-9]*$". -->
			<metadata name="altname" value="TypeName" />
			<property name="severity" value="warning" />
		</module>

		<module name="ConstantNameCheck">
			<!-- Validates non-private, static, final fields against the supplied 
				public/package final fields "^[A-Z][A-Z0-9]*(_[A-Z0-9]+)*$". -->
			<metadata name="altname" value="ConstantName" />
			<property name="applyToPublic" value="true" />
			<property name="applyToProtected" value="true" />
			<property name="applyToPackage" value="true" />
			<property name="applyToPrivate" value="false" />
			<property name="format" value="^([A-Z][A-Z0-9]*(_[A-Z0-9]+)*|FLAG_.*)$" />
			<message key="name.invalidPattern"
				value="Variable ''{0}'' should be in ALL_CAPS (if it is a constant) or be private (otherwise)." />
			<property name="severity" value="warning" />
		</module>

		<module name="StaticVariableNameCheck">
			<!-- Validates static, non-final fields against the supplied expression 
				"^[a-z][a-zA-Z0-9]*_?$". -->
			<metadata name="altname" value="StaticVariableName" />
			<property name="applyToPublic" value="true" />
			<property name="applyToProtected" value="true" />
			<property name="applyToPackage" value="true" />
			<property name="applyToPrivate" value="true" />
			<property name="format" value="^[a-z][a-zA-Z0-9]*_?$" />
			<property name="severity" value="warning" />
		</module>

		<module name="MemberNameCheck">
			<!-- Validates non-static members against the supplied expression. -->
			<metadata name="altname" value="MemberName" />
			<property name="applyToPublic" value="true" />
			<property name="applyToProtected" value="true" />
			<property name="applyToPackage" value="true" />
			<property name="applyToPrivate" value="true" />
			<property name="format" value="^[a-z][a-zA-Z0-9]*$" />
			<property name="severity" value="warning" />
		</module>

		<module name="MethodNameCheck">
			<!-- Validates identifiers for method names. -->
			<metadata name="altname" value="MethodName" />
			<property name="format" value="^[a-z][a-zA-Z0-9]*(_[a-zA-Z0-9]+)*$" />
			<property name="severity" value="warning" />
		</module>

		<module name="ParameterName">
			<!-- Validates identifiers for method parameters against the expression 
				"^[a-z][a-zA-Z0-9]*$". -->
			<property name="severity" value="warning" />
		</module>

		<module name="LocalFinalVariableName">
			<!-- Validates identifiers for local final variables against the expression 
				"^[a-z][a-zA-Z0-9]*$". -->
			<property name="severity" value="warning" />
		</module>

		<module name="LocalVariableName">
			<!-- Validates identifiers for local variables against the expression 
				"^[a-z][a-zA-Z0-9]*$". -->
			<property name="severity" value="warning" />
		</module>


		<!-- LENGTH and CODING CHECKS -->

		<module name="LineLength">
			<!-- Checks if a line is too long. -->
			<property name="max"
				value="${com.puppycrawl.tools.checkstyle.checks.sizes.LineLength.max}"
				default="100" />
			<property name="severity" value="error" />

			<!-- The default ignore pattern exempts the following elements: - import 
				statements - long URLs inside comments -->

			<property name="ignorePattern"
				value="${com.puppycrawl.tools.checkstyle.checks.sizes.LineLength.ignorePattern}"
				default="^(package .*;\s*)|(import .*;\s*)|( *\* *https?://.*)$" />
		</module>

		<module name="LeftCurly">
			<!-- Checks for placement of the left curly brace ('{'). -->
			<property name="severity" value="warning" />
		</module>

		<module name="RightCurly">
			<!-- Checks right curlies on CATCH, ELSE, and TRY blocks are on the same 
				line. e.g., the following example is fine: <pre> if { ... } else </pre> -->
			<!-- This next example is not fine: <pre> if { ... } else </pre> -->
			<property name="option" value="same" />
			<property name="severity" value="warning" />
		</module>

		<!-- Checks for braces around if and else blocks -->
		<module name="NeedBraces">
			<property name="severity" value="warning" />
			<property name="tokens"
				value="LITERAL_IF, LITERAL_ELSE, LITERAL_FOR, LITERAL_WHILE, LITERAL_DO" />
		</module>

		<module name="UpperEll">
			<!-- Checks that long constants are defined with an upper ell. -->
			<property name="severity" value="error" />
		</module>

		<module name="FallThrough">
			<!-- Warn about falling through to the next case statement. Similar to 
				javac -Xlint:fallthrough, but the check is suppressed if a single-line comment 
				on the last non-blank line preceding the fallen-into case contains 'fall 
				through' (or some other variants which we don't publicized to promote consistency). -->
			<property name="reliefPattern"
				value="fall through|Fall through|fallthru|Fallthru|falls through|Falls through|fallthrough|Fallthrough|No break|NO break|no break|continue on" />
			<property name="severity" value="error" />
		</module>


		<!-- MODIFIERS CHECKS -->

		<module name="ModifierOrder">
			<!-- Warn if modifier order is inconsistent with JLS3 8.1.1, 8.3.1, and 
				8.4.3. The prescribed order is: public, protected, private, abstract, static, 
				final, transient, volatile, synchronized, native, strictfp -->
		</module>


		<!-- WHITESPACE CHECKS -->

		<module name="WhitespaceAround">
			<!-- Checks that various tokens are surrounded by whitespace. This includes 
				most binary operators and keywords followed by regular or curly braces. -->
			<property name="tokens"
				value="ASSIGN, BAND, BAND_ASSIGN, BOR,
        BOR_ASSIGN, BSR, BSR_ASSIGN, BXOR, BXOR_ASSIGN, COLON, DIV, DIV_ASSIGN,
        EQUAL, GE, GT, LAND, LE, LITERAL_CATCH, LITERAL_DO, LITERAL_ELSE,
        LITERAL_FINALLY, LITERAL_FOR, LITERAL_IF, LITERAL_RETURN,
        LITERAL_SYNCHRONIZED, LITERAL_TRY, LITERAL_WHILE, LOR, LT, MINUS,
        MINUS_ASSIGN, MOD, MOD_ASSIGN, NOT_EQUAL, PLUS, PLUS_ASSIGN, QUESTION,
        SL, SL_ASSIGN, SR_ASSIGN, STAR, STAR_ASSIGN" />
			<property name="severity" value="error" />
		</module>

		<module name="WhitespaceAfter">
			<!-- Checks that commas, semicolons and typecasts are followed by whitespace. -->
			<property name="tokens" value="COMMA, SEMI, TYPECAST" />
		</module>

		<module name="NoWhitespaceAfter">
			<!-- Checks that there is no whitespace after various unary operators. 
				Linebreaks are allowed. -->
			<property name="tokens"
				value="BNOT, DEC, DOT, INC, LNOT, UNARY_MINUS,
        UNARY_PLUS" />
			<property name="allowLineBreaks" value="true" />
			<property name="severity" value="error" />
		</module>

		<module name="NoWhitespaceBefore">
			<!-- Checks that there is no whitespace before various unary operators. 
				Linebreaks are allowed. -->
			<property name="tokens" value="SEMI, DOT, POST_DEC, POST_INC" />
			<property name="allowLineBreaks" value="true" />
			<property name="severity" value="error" />
		</module>

		<module name="ParenPad">
			<!-- Checks that there is no whitespace before close parens or after open 
				parens. -->
			<property name="severity" value="warning" />
		</module>

                <module name="Indentation">
                        <!-- Checks code indentation -->
                        <property name="basicOffset" value="2" />
                </module>
	</module>
</module>